It has become customary in automobiles, sport utility vehicles and other vehicles to utilize a stop/brake light which is located high on the rear of the vehicle and is centered for improved visibility. The stop light is commonly known as a center high mount stop light (CHMSL). The stop light may, for example, be located in the rear window. In sport utility vehicles which have a tailgate, the stop light may be located above the rear window. Such stop lights are typically elongated and may be twenty or more inches long. In order to achieve uniform illumination over this length, neon lamps may be used. In general, neon lamps have relatively low power consumption and long operating lives.
It has proposed in the prior art to use neon lamps for signaling in vehicles. A neon lamp direction signal, including arrows for indicating direction, is disclosed in U.S. Pat. No. 1,792,599 issued Feb. 17, 1931 to Murray. The disclosed lamp also includes a stop signal indication. A neon sign, including a neon lamp tube for mounting in the window of an automobile, is disclosed in U.S. Pat. No. 1,854,654 issued Apr. 19, 1932 to Koch, Jr. et al. A neon lamp signaling device for mounting in the rear window of the vehicle is disclosed in U.S. Pat. No. 1,839,499 issued Jan. 5, 1932 to Rava. A rare gas automobile indicator light system employing a single, horizontally-disposed indicator tube operated to provide braking, parking, emergency flasher and turn indication is disclosed in U.S. Pat. No. 4,682,146 issued Jul. 21, 1987 to Friedman, III.
For efficient operation, the CHMSL should have a relatively narrow output light pattern in a plane parallel to the direction of vehicle travel, so that the stop light is clearly visible to following vehicles. Typically, the stop light is required to have an output of 16 candela or greater at 10.degree. up from the horizontal plane, 25 candela or greater at 5.degree. up from horizontal and 25 candela or greater at 5.degree. down from horizontal. A lens is usually used to produce the desired light pattern.
It has been proposed to use aperture lamps in CHMSL's. In an aperture lamp, a tubular neon lamp is coated on its outside surface with a reflecting material, except for a narrow strip, or aperture, along the length of the tube. Light generated within the lamp tube is reflected, except in the region of the aperture. Thus, light is emitted from the lamp only through the aperture. Aperture lamps are widely used in xerographic applications. Fluorescent aperture lamps are disclosed, for example, in U.S. Pat. No. 3,225,241 issued Dec. 21, 1965 to Spencer et al; U.S. Pat. No. 3,012,168 issued Dec. 5, 1961 to Ray et al; U.S. Pat. No. 3,987,331 issued Oct. 19, 1976 to Schreurs; U.S. Pat. No. 3,275,872 issued Sep. 28, 1966 to Chernin et al; U.S. Pat. No. 3,115,309 issued Dec. 24, 1963 to Spencer et al; U.S. Pat. No. 3,067,351 issued Dec. 4, 1962 to Gungle et al; U.S. Pat. No. 3,717,781 issued Feb. 20, 1973 to Sadoski et al; and U.S. Pat. No. 3,886,396 issued May 27, 1975 to Hammer et al.
Aperture lamps fabricated by coating the lamp envelope with a reflective material have several drawbacks. The lamp envelope coating process is an additional step in the lamp fabrication process and adds to its cost. In addition, steps must be taken during the assembly of the aperture lamp into a lamp fixture to ensure that the aperture is accurately aligned with the optical axis of the lamp fixture. It is therefore desirable to provide lamp assemblies which overcome these drawbacks.